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PDBsum entry 5m3m
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Transcription
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PDB id
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5m3m
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Contents |
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1462 a.a.
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1166 a.a.
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305 a.a.
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212 a.a.
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98 a.a.
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131 a.a.
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116 a.a.
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69 a.a.
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101 a.a.
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44 a.a.
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97 a.a.
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131 a.a.
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58 a.a.
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192 a.a.
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References listed in PDB file
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Key reference
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Title
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Structure of RNA polymerase I transcribing ribosomal DNA genes.
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Authors
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S.Neyer,
M.Kunz,
C.Geiss,
M.Hantsche,
V.V.Hodirnau,
A.Seybert,
C.Engel,
M.P.Scheffer,
P.Cramer,
A.S.Frangakis.
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Ref.
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Nature, 2016,
540,
607-610.
[DOI no: ]
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PubMed id
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Abstract
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RNA polymerase I (Pol I) is a highly processive enzyme that transcribes
ribosomal DNA (rDNA) and regulates growth of eukaryotic cells. Crystal
structures of free Pol I from the yeast Saccharomyces cerevisiae have revealed
dimers of the enzyme stabilized by a 'connector' element and an expanded cleft
containing the active centre in an inactive conformation. The central bridge
helix was unfolded and a Pol-I-specific 'expander' element occupied the
DNA-template-binding site. The structure of Pol I in its active transcribing
conformation has yet to be determined, whereas structures of Pol II and Pol III
have been solved with bound DNA template and RNA transcript. Here we report
structures of active transcribing Pol I from yeast solved by two different
cryo-electron microscopy approaches. A single-particle structure at 3.8 Å
resolution reveals a contracted active centre cleft with bound DNA and RNA, and
a narrowed pore beneath the active site that no longer holds the
RNA-cleavage-stimulating domain of subunit A12.2. A structure at 29 Å
resolution that was determined from cryo-electron tomograms of Pol I enzymes
transcribing cellular rDNA confirms contraction of the cleft and reveals that
incoming and exiting rDNA enclose an angle of around 150°. The structures
suggest a model for the regulation of transcription elongation in which
contracted and expanded polymerase conformations are associated with active and
inactive states, respectively.
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